1. Field of the Invention
This invention relates to rotary shredder apparatus with provision for ejecting hard to shred waste in a self-clearing cycle.
2. Description of the Prior Art
It is well understood in the processing of waste material, like municipal waste, that large uncrushables and hard to shred material is encountered. In instances when the uncrushables and hard to shred material is encountered the shredder jams the shafts on which the shredding, cutting and ripping discs are carried. Often the apparatus must be stopped and the material causing the jam removed by hand. The hand unloading results in loss of productivity of the apparatus to reduce the waste material.
Shredder apparatus known to have means for relieving jams when material gets into the shredding cutters is exemplified by Culbertson, et al U.S. Pat. No. 4,034,918 of July 1977 and by Cunningham, et al U.S. Pat. No. 3,808,062 of Feb. 25, 1975. However, in these examples, the apparatus is operated in a series of shaft reversal cycles in an effort to shred or reduce the offending material sufficiently to eventually send it through the apparatus. The foregoing examples have led to the type of shredding machine which is able to disgorge the hard to shred material, as disclosed in Hardwick et al U.S. Pat. No. 4,351,485 of Sept. 28, 1982. In this patent the shredding shafts are not in a common plane but the plane is inclined to the horizontal so one shaft is lower than the other. Upon shaft reversal the lowest shaft is rotated in a direction to move the material through a side door which opens upon shaft reversal. In this manner, hard to shred or cut material is moved out of the hopper.
A problem with the apparatus of U.S. Pat. No. 4,351,485 is that material may not clear from the higher one of the shafts and upon reversal of both shafts, the highest shaft can retain or withhold the unwanted material away from the lower shaft. Another problem is that the waste material can accumulate over the lower shaft position which results in an uneven distribution of the waste material in the hopper which can prolong the time necessary to process the material as the high shaft works against the low shaft.